1. Field of the Invention
This invention relates to a composition that is used as a catalyst and a solvent in acid catalysis processes.
It also relates to acid catalysis processes that use said composition, and more particularly the alkylation of aromatic hydrocarbons, the oligomerization of olefins, the dimerization of isobutene, the alkylation of olefins by isoparaffins, the isomerization of n-paraffins into isoparaffins, the isomerization of n-olefins into iso-olefins, the isomerization of the double bond of an olefin and the purification of a mixture of olefins containing branched alpha olefins as impurities.
2. Description of the Prior Art
The acid catalysis reactions are very important industrial reactions that can be applied in the field of refining and petrochemistry. As an example, the case of the alkylation of aromatic hydrocarbons will be cited, in particular for the production of LABs (for “linear alkyl benzenes”), which are the first intermediate products for the synthesis of biodegradable detergents.
The acid catalysts that are used by the conventional methods, in particular for the alkylation of aromatic hydrocarbons, are Lewis and/or Broensted acids. The most commonly used are hydrofluoric acid (HF), concentrated sulfuric acid (H2SO4), boron trifluoride (BF3), aluminum trichloride (AlCl3), solid catalysts such as zeolites, or the combination of these different acids. The use of these acids, however, exhibits drawbacks, in particular due to increasingly strict measures aimed at environmental protection. For example, the toxic, volatile and corrosive use of HF involves deploying important safety measures regarding operators and equipment. Low-activity concentrated sulfuric acid requires the use of large volumes of acid that generate waste, essentially inorganic salts, which should be brought under environmental standards before being rejected. Aluminum trichloride, nevertheless more widely used industrially, pure or made complex with a base (often called “red oils”), is consumed in a large amount. In addition, this type of catalyst is not easily separated from the products of the reaction. The recovery of products is then carried out after the catalyst is destroyed, which, on the one hand, generates large amounts of waste, and, on the other hand, is reflected by an additional cost for the process. Consequently, an intensive study for replacing these catalysts is currently being developed.
The solid catalysts such as the zeolites provide an improvement in connection with the separation of the products and the recycling of the catalyst but impose reaction temperatures that are often higher.
In contrast, it is known that the isobutene dimers (trimethyl-2,4,4-pentene-1 and −2) are advantageous intermediate products for the production of different products that have a commercial advantage. By way of examples, it is possible to cite higher alcohols, aldehydes, and acids.
Trimethyl-2,2,4-pentane can be obtained by hydrogenation of trimethylpentenes and constitutes an additive that is sought for the reformulation of gasolines [absence of sulfur, aromatic compound and olefin and low volatility are added to a high octane number: engine octane number (RON)=research octane number (RON)=100].
The selective dimerization of the isobutene, followed by a hydrogenation of the products that are obtained from trimethyl-2,2,4-pentane that have a high octane number, constitutes an advantageous method that makes it possible                i. To replace the MTBE (methyl-tert-butyl-ether: RON=118; MON=100), now banned in California for environmental reasons, and        ii. To use isobutene, obtained from C4 fractions of the catalytic cracking (FCC) or steam-cracking processes, raw material in the production of MTBE.        
The dimerization (oligomerization) of isobutene is an exothermic reaction that is catalyzed by acids. Various acids have been described in literature such as sulfuric acid or its derivatives, chlorinated or fluorinated aluminas, zeolites, silica-aluminas, etc. The acids most typically used in the industry, however, are phosphoric acid (generally supported or “solid phosphoric acid” SAP) and ion-exchange resins (“ion exchange resins” IER, SP-isoether process that is licensed by Snamprogetti or the InAlk process proposed by UOP).
The primary difficulty that is linked to these processes is obtaining a good dimer selectivity. Actually, the exothermicity of the reaction is often difficult to monitor and entrains the formation of oligomers (essentially C12 olefins and C16 olefins) that are obtained by parallel reactions from isobutene. These oligomers have boiling points that are too high and are beyond or at the limit of specifications that are required for reformulated gasolines. Furthermore, these oligomers contribute to deactivating the catalysts.
Various works in literature describe certain solutions for reducing the formation of these oligomers.
In the case of ion-exchange resins (Amberlyst-15 or -35 type), the use of a diluent (or solvent) is often recommended. The selectivity of dimers depends on the choice of this solvent. The most effective additives are alcohols (U.S. Pat. Nos. 5,877,372; 4,100,220) that lead to the co-production of ethers, or the ethers (in U.S. Pat. No. 4,447,668, MTBE, ETBE, etc.). It is possible to cite the works of Snamprogetti (M. Marchionna and al. Catal. Today, 65 (2001) 397-403, GB-A-2 325 237) who studied the influence of the addition of MTBE or MeOH for the purpose of reusing the existing units of MTBE. Advantageous trimethylpentene selectivities can thus be attained but with the conversion of isobutene, the selectivities are often less than 85%.
International Patent Application WO-A-01/51 435 describes a process scheme in which the isobutene is produced by dehydration of tert-butyl alcohol. The isobutene is dimerized preferably by an Amberlyst A-15®-type resin in the presence of tert-butyl alcohol (selectivity promoter) and alkane (butane or isobutane) as a diluent. The presence of occupied alcohol puts the formation of ether at a disadvantage but also reduces the reaction speed.
International Patent Application WO-A-01/46 095 describes a process for producing isooctanes from a C4 fraction with a catalyst that comprises a beta zeolite that makes it possible to convert isobutene selectively in the presence of butenes (conversion of butenes<10%). The C8 selectivities that are described in the examples, however, do not exceed 60%. Furthermore, the service life of the catalyst is not described.
All of the processes that are described above have limitations such as trimethylpentene selectivities that are still too low for high conversions per pass of isobutene, which requires, for example, a recycling of isobutene and increases the cost of the process. The risks of premature deactivation of the catalyst by “fouling” by heavier oligomers or by the impurities that are contained in the feedstocks exist, and the service life of the sulfonic resins is consequently shorter for the production of trimethylpentenes than for the synthesis of MTBE.
It is also known that there is a large variety of catalysts that make it possible to isomerize the double bond of the olefins. This is not surprising, moreover, since it is one of the easiest reactions among the reactions for transformation of the hydrocarbons and since the thermodynamics of the reaction are favorable to the formation of internal olefins at low temperatures. By way of examples, it is possible to cite the isomerization of butene-1 into butene-2 (U.S. Pat. No. 5,237,120 that uses modified zeolites) or else the isomerization of linear alpha olefins (for example C12-C18 in U.S. Pat. No. 4,749,819) for producing internal olefins. However, despite the diversity of existing catalysts, the difficulty remains of carrying out the isomerization of the double bond of the olefin with a good activity without, however, producing (or by reducing the production of) undesirable by-products from oligomers of the olefin.
Finally, numerous industrial processes produce alpha linear olefins that are mixed with internal linear olefins and branched alpha olefins. The branched alpha olefins that are being considered, also called vinylidene olefins, are those that correspond to general formula CH2═CRR′, in which R and R′ designate alkyl radicals.
Based on the application (for example the production of detergents, co-monomers for the production of low-density linear polyethylenes—or LLDPE—or precursors for the synthesis of alcohols or aldehydes), it is desirable to have the highest purity possible of linear olefins. The separation of the linear olefins from the branched olefins is not easy, particularly when these olefins have the same molecular weight and similar boiling points. Various patents (U.S. Pat. Nos. 5,789,646; 5,095,172; WO-A-99/29 641) describe the separation of vinylidene olefins from a mixture of linear olefins.
The non-aqueous ionic liquids of composition Q+A− are the object of several reviews (for example, T. Welton, Chem. Rev. 1999, 99, 2071). They can be applied in numerous ways as solvents for catalysis by transition metals or as extraction solvents for carrying out liquid-liquid extractions. Their use as solvents and acid catalysts has primarily been described for ionic liquids of organochloroaluminate acid type and applied to the alkylation of aromatic hydrocarbons. Thus, Patent Applications WO-A-95/21806, WO-A-98/03454 and WO-A-00/41809 describe processes for producing alkylaromatic compounds, such as LABs, for example dodecylbenzene from benzene and dodecene, or ethylbenzene by reaction of benzene with ethylene and documents EP-A-693088 and EP-B-576323 of the processes for conversion of olefins by acid catalysis, which, as a whole, use as catalysts non-aqueous ionic liquids that result from bringing into contact quaternary ammonium halides and/or halohydrates of primary, secondary or tertiary amine and/or quaternary phosphonium halides with a Lewis acid such as an aluminum halide, such as, for example, aluminum trichloride. These liquid catalysts can also be, in an improved way, pre-mixed with aromatic hydrocarbon.
The non-aqueous ionic liquids can also be applied to the alkylation of olefins by isobutane (U.S. Pat. No. 5,750,455) or to the production of synthetic lubricants (EP-A-791 643).
The advantage of these liquid catalytic systems is that they are not very miscible with the products of the reaction, whereby the latter can be separated by decanting. The catalytic phase can then be recycled and reused, and the consumption of catalyst is thus reduced. These systems, however, also present limitations. For example, these ionic media are moisture-sensitive. In the presence of protons, the ionic medium can generate hydrochloric acid by reaction with the AlCl3 that is potentially present in the medium, which can entrain the formation of chlorinated organic impurities and can contaminate the products.
Patent Application WO-A-00/16 902 describes the use of an ionic liquid that does not contain the Lewis acidity that is obtained by reaction of a nitrogenous compound (for example an amine or a quaternary ammonium) or phosphorus compound with a Broensted acid in amounts such that the ratio of said nitrogenous compound or phosphorus compound to the acid is less than 1/1. These media are used for catalyzing in particular the alkylation of benzene with decene-1.